In detonating a plurality of blasting charges, transmission tubes may be deployed from a remote initiating point to transmit initiation signals to detonate individual explosive charges. Although transmission tubes have been primarily used for blast initiation in mining and quarrying applications, there are a number of other uses for transmission tubes. For example, transmission tubes have been used to transmit an automotive collision impact signal to activate a protective airbag or pre-tensioning automotive safety belts.
The aforementioned transmission tubes may be of the type disclosed in U.S. Pat. No. 3,590,739 sold under the trademark “Nonel” and sometimes referred to as “shock tube”. An improved transmission tube design is disclosed in U.S. Pat. No. 4,328,753 and consists of an inner adhesive plastic layer to secure the explosive composition and an outer abrasion resistant plastic layer. As used herein, the term “transmission tube” refers to any detonating or deflagrating signal transmission tube or line including a flexible hollow tube, which can carry a detonating or deflagrating signal along its interior, which signal does not destroy the tube.
The term “signal” when used in connection with the aforementioned transmission tube is intended to refer to either the detonating shock wave or the deflagrating flame front, which is transmitted along the interior of the tube, by combustion of a reactive substance, contained therein.
In transmitting a signal in the field, the reliability of transmission tubes may be inadvertently reduced. For example, when deploying the product a sharp rock or other object may penetrate the wall of the transmission tube allowing water to enter the tube and causing a signal transmission failure.
It is therefore an object of the invention to provide a signal transmission device having improved reliability of signal transmission.
It is a further object of the invention to provide a reliable signal transmission device, capable of transmitting a plurality of signals, that is easy to handle and rapidly deploy.
It is a further object of the invention to provide a reliable signal transmission device that is easy to manufacture and facile in its use.
Other objects will be in part obvious and in part pointed out in more detail hereinafter.
A better understanding of the objects, advantages, features, properties and relations of the invention will be obtained from the following description and accompanying drawings which set forth certain illustrative embodiments and are indicative of the various ways in which the principles of the invention are employed.